Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$66.27	7.481%	$71.2277	$71.23	$71.25	$71.20
Purchase #2	$188.98	3.387%	$195.3808	$195.38	$195.40	$195.40
Purchase #3	$145.80	4.598%	$152.5039	$152.50	$152.50	$152.50
Purchase #4	$245.54	9.209%	$268.1518	$268.15	$268.15	$268.20
Purchase #5	$174.57	12.544%	$196.4681	$196.47	$196.45	$196.50
Purchase #6	$185.72	4.575%	$194.2167	$194.22	$194.20	$194.20
Purchase #7	$235.80	4.194%	$245.6895	$245.69	$245.70	$245.70
7 purchase totals =	$1,242.68		$1,323.6385	$1,323.64	$1,323.65	$1,323.70